Spin tunneling of trigonal and hexagonal ferromagnets in an arbitrarily directed magnetic field

Abstract

The quantum tunneling of the magnetization vector are studied theoretically in single-domain ferromagnetic nanoparticles placed in an external magnetic field at an arbitrarily directed angle in the $ZX$ plane. We consider the magnetocrystalline anisotropy with trigonal and hexagonal crystal symmetry, respectively. By applying the instanton technique in the spin-coherent-state path-integral representation, we calculate the tunnel splittings, the tunneling rates and the crossover temperatures in the low barrier limit for different angle ranges of the external magnetic field (${\theta }_H=\pi /2$, $\pi /2\ll {\theta }_H\ll \pi$, and ${\theta }_H=\pi$). Our results show that the tunnel splittings, the tunneling rates and the crossover temperatures depend on the orientation of the external magnetic field distinctly, which provides a possible experimental test for magnetic quantum tunneling in nanometer-scale single-domain ferromagnets.

31 pages, 3 figures, accepted by J. Phys.: Conden. Matter

Cited by in corpus (1)

• Intermediate spin, Schrödinger cat states and nano-magnets